Help please? How much time does it take for carbon monoxide to affect you?

Instantaneous. Carbon monoxide does damage by binding to red blood cells, causing them to not be able to carry oxygen. It happens as soon as the CO contacts the blood and it will stay attached to the hemoglobin in the blood for many hours. It is reversed much faster when the person is treated by breathing 100% oxygen. It's normal to have a little CO in the blood - smokers have up to 15% (40% is lethal)